See the attached synoptic chart. The surface wind to be expected at YPPH at the time of the chart is:
a) cold southwesterly
b) cold northwesterly
c) warm southeasterly
d) warm southwesterly
My answer: B
Correct answer: D
I thought the low just southwest of YPPH will be bringing cold air from lower latitudes towards YPPH, therefore I chose B. Or is the air still not "cold" yet until the cold front passes so the answer is D?
The cold front marks the boundary between the warm continental air mass over Australia and the cold polar air mass behind the front.
At the time of the chart, the wind at Perth would be north-westerly and warm. When the front passes over Perth the wind will back to be come a cold south-westerly.
The passage of a cold front usually brings a backing of the wind, generally from west or north-west, fairly rapidly to south or south-west. Sometimes associated with a squall line in the warm sector along the frontal boundary.
